Distribution of RF signals is particularly difficult inside buildings and in complex areas, where obstacles scatter or absorb RF radiation. In-building distribution systems consist of two major parts: a set of repeater antennas and accessories required for re-transmitting RF signals inside buildings, and a cabling system such as an optical fiber network for interconnecting the in-building antennas with a main antenna. The main antenna is usually installed on top of the building, while the repeaters are located within various rooms inside the building.
The cost of installing in-building distribution networks is generally very high, and includes the cost of multiple repeater antennas, associated electronics, and links, as well as the cost of installing the antennas and suitable links. It is desirable that the signal processing electronics used at the repeater sites be simple, robust, and inexpensive. It is also desirable that the signals distributed through the network be compatible with pre-existing in-building wiring infrastructure, since installing specialized links can be prohibitively expensive.
The above-referenced parent U.S. patent application Ser. No. 08/635,368 describes a system for distributing high-frequency signals using repeaters connected to a central station by low-bandwidth transmission lines. The transmission lines are unsuitable for transmitting the high-frequency signals. The signals are down-converted, transmitted to the repeaters over the transmission lines, up-converted, and emitted. Low-stability, inexpensive oscillators used for down- and up-conversion are frequency-stabilized using a single, central high-stability oscillator.
In U.S. Pat. No. 5,603,080, herein incorporated by reference, Kallander et al. describe a repeater system for use in complex environments. The system comprises two-way frequency converters for down-converting a centrally received high-frequency signal, and recovering the signal at remote locations by up-conversion. The system described by Kallander et al. re-transmits the entire frequency band of the received signal.